1. Field of the Invention
The present invention relates to a cathode ray tube glass coated with a water-soluble coating film, a method for producing the cathode ray tube glass, and a method for cleaning the cathode ray tube glass.
2. Description of the Background
For avoiding or removing contaminants attached to a surface of a cathode ray tube glass such as a panel glass, a funnel glass and so on during manufacture, processing, storage and transportation of it, there have been practiced: (1) a method for cleaning the atmosphere around such glass; (2) a method for preventing such glass from the contact with a container for storage and so on; (3) a method for preventing the deposition of contaminants due to material existing around such glass; and (4) a method for removing contaminants by a washing treatment having a physical or chemical effect before a necessary operation. Further, as a new cleaning method utilizable generally for glass, there has been proposed such a method that a coating film is formed by applying previously a water-soluble salt on a glass surface so that contaminants which may be attached onto the coating film are dissolved and removed together with the coating film by washing (JP-A-6-340865).
Various surface treatments such as coating of a fluorescent material, coating of an electric conductive graphite, coating of an antireflection film and so on are conducted to a surface of the cathode ray tube glass. In this case, when a slight amount of contaminants are attached to the surface, water repellency is effected to thereby cause difficulty in conducting the normal coating operations. Even though the coating operations have been completed, there is still a danger of inducing a defect in patterning a fluorescent material or an insufficient electric strength owing to remaining contaminants. Therefore, an extremely high cleanness is required for the cathode ray tube glass in comparison with a glass product for another usage.
The cathode ray tube glass comprises generally a panel glass and a funnel glass. FIG. 1 shows a construction of the cathode ray tube glass wherein reference numeral 1 designates a funnel glass, numeral 2 a panel glass, numeral 3 a funnel portion, numeral 4 a neck tube portion, numeral 5 a seal edge portion, numeral 6 a pin, numeral 7 an anode button, and numeral 8 a face portion. Hereinbelow, a body formed by sealing the neck tube portion to the funnel portion is simply referred to as the funnel glass.
Generally, glass products such as panel glass, funnel portions, neck tube portions and so on, after having been shaped and processed, are transported to and stored in a warehouse or the like for a predetermined term until they undergo joining and sealing operations or surface treatments. Accordingly, it is very difficult to completely avoid contamination due to a slight amount of contaminants which may be attached to a glass surface of them even though care is taken for cleaning the atmosphere around the glass products or choosing a suitable wrapping material in order to avoid such contamination.
Further, once the contaminants have attached to the glass surface, reactions occur on the glass surface with a lapse of time to increase an adhesive force. Accordingly, in many cases, the contaminants on the glass surface can not be removed by simply washing operations. It is, therefore, necessary to conduct washing with a strong acid or alkali such as hydrofluoric acid or sodium hydroxide or the like, or to use above-mentioned washing with another washing operation utilizing a physical effect. However, these forcible washing operations are troublesome in use; an increase of cost is invited and there is a danger of causing an additional defect on the glass surface which have been finely processed. Further, these forcible operations cause difficulty in draining a waste solution from the standpoint of environmental protection.
The technique disclosed in JP-A-6-340865 does not mention in a concrete manner such means for providing an excellent cleaning performance required for the cathode ray tube glass or eliminating an adverse effect, to a TV characteristic, caused by a water-soluble material which may remain on the glass surface.